[cleanup] Cleanup docs and other stuff on new thread-local actors

[slawlor]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 85.58559% with 32 lines in your changes missing coverage. Please review.

Project coverage is 80.95%. Comparing base (56e12a6) to head (820104c).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
ractor/src/thread_local/supervision_tests.rs	85.56%	27 Missing ⚠️
ractor/src/thread_local.rs	84.84%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #350      +/-   ##
==========================================
+ Coverage   80.60%   80.95%   +0.34%     
==========================================
  Files          69       70       +1     
  Lines       14156    14367     +211     
==========================================
+ Hits        11411    11631     +220     
+ Misses       2745     2736       -9     

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